Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$187.28	12.868%	$211.3792	$211.38	$211.40	$211.40
Purchase #2	$91.50	9.839%	$100.5027	$100.50	$100.50	$100.50
Purchase #3	$13.77	11.533%	$15.3581	$15.36	$15.35	$15.40
Purchase #4	$248.51	3.174%	$256.3977	$256.40	$256.40	$256.40
Purchase #5	$9.74	13.750%	$11.0793	$11.08	$11.10	$11.10
Purchase #6	$55.36	8.685%	$60.168	$60.17	$60.15	$60.20
Purchase #7	$28.72	11.844%	$32.1216	$32.12	$32.10	$32.10
7 purchase totals =	$634.88		$687.0066	$687.01	$687.00	$687.10